A modulation-insensitive dual-mode waveguide optical switch and a preparation method thereof

Abstract

The application discloses a modulation-insensitive dual-mode waveguide optical switch and a preparation method thereof, and belongs to the technical field of planar optical waveguide devices. The switch is composed of a silicon wafer substrate, a polymer lower cladding layer, a polymer optical waveguide core layer and a polymer upper cladding layer from bottom to top, the polymer optical waveguide core layer is covered in the polymer upper cladding layer, and the refractive index of the polymer optical waveguide core layer is higher than that of the polymer upper cladding layer and the polymer lower cladding layer. The application utilizes the advantages of simple asymmetric directional coupling structure and asymmetric Y branch structure and the large thermal-optical coefficient of organic polymer materials, and realizes the modulation-insensitive switch of two signal optical modes through mode conversion by using the asymmetric Y branch when the heating electrode is modulated. The preparation process of the application is simple, only needs spin coating, photoetching and wet etching, effectively reduces the production cost, improves the production efficiency of the device, is favorable for large-scale batch production, and enables the mode signal optical switch to be applied to actual use.

Description

Technical Field

[0001] This invention belongs to the field of planar optical waveguide device technology, specifically relating to a modulation-insensitive dual-mode waveguide optical switch and its fabrication method. Background Technology

[0002] Faced with the exponential growth of global information volume, people's demands for information transmission speed and bandwidth are constantly increasing. To address this situation, various solutions are being actively proposed to expand communication bandwidth and meet the challenges posed by nonlinear limitations, thereby promoting the innovative development of high-speed signal processing systems. Therefore, optical signal interconnection has become key to solving this problem. Compared to traditional electrical interconnection, optical signal interconnection uses signal light as the medium for information transmission. Signal light has a faster transmission speed, thus effectively improving information transmission speed and communication capacity. However, traditional single-mode optical signal communication is limited by the nonlinear effects and Shannon limit of optical fibers, making it difficult to further increase communication capacity. To solve this problem, researchers have proposed various multiplexing technologies such as wavelength division multiplexing (WDM), partial division multiplexing (PDM), and mode division multiplexing (MDM). The advantage of MDM lies in its significant improvement in the performance and efficiency of optical signal communication systems. By allowing multiple different modes of signal light to be transmitted in the same optical fiber, it greatly increases the network's transmission capacity, enabling the network to handle more data traffic simultaneously to meet people's ever-increasing communication needs. Since the signals of each mode are independent of each other, a failure in a single mode will not affect the transmission of other modes. Therefore, the modulus division multiplexing system has stronger fault tolerance and provides more reliable communication services.

[0003] Mode-mode optical switches play a crucial role in optical signal communication systems and are one of the important components in mode-division multiplexing (MDD) systems. Traditional mode-mode optical switch systems suffer from large device size and high power consumption because modulating the signal light requires a mode demultiplexer to convert the signal optical mode into the fundamental mode, followed by operation using a separate optical switch. To overcome these limitations, there is an urgent need to develop novel mode-mode optical switches capable of flexibly switching multiple signal optical modes at the same modulation power. This would effectively improve the capacity and flexibility of optical signal communication systems while reducing system complexity.

[0004] Mode-dependent optical switches based on planar waveguide structures offer several advantages over fiber-optic mode-dependent optical switches. They not only exhibit excellent compatibility with fiber optics and a more compact structure with lower insertion loss, but also reduce mode-dependent loss. Their high integration and flexible design make them more convenient for practical applications. The use of traditional photolithography and etching processes simplifies mass production. To enhance flexibility, techniques such as electro-optical effects and thermo-optical effects can be used to modulate the phase of the signal light, enabling more flexible switching functions.

[0005] Waveguide-type mode signal optical switches come in various types depending on their material systems. Silicon dioxide / silicon devices possess a large refractive index difference, enabling miniaturization and integration, but their manufacturing is complex and costly. In contrast, polymer-based devices are simple to manufacture, inexpensive, compatible with semiconductor processes, and can be functionally doped. Polymer materials have a large thermo-optic coefficient and low thermal conductivity, allowing for modulation of devices through thermo-optical effects with low power consumption. Therefore, mode signal optical switches manufactured using these characteristics offer advantages such as flexible structure and low power consumption. However, traditional mode signal optical switches mostly only allow for selectable modulation of one mode, and the modulation power required for different modes varies, preventing the modulation of two or more modes at the same power, thus limiting the application range of mode signal optical switches. Summary of the Invention

[0006] To overcome the shortcomings of traditional optical switches with different modulation powers, the present invention aims to provide a modulation-insensitive dual-mode waveguide optical switch and its fabrication method.

[0007] This invention cascades traditional asymmetric directional coupled waveguide structures and asymmetric Y-branch optical waveguide structures. In the structural design of planar optical waveguide devices, both asymmetric directional coupled waveguide structures and asymmetric Y-branch optical waveguide structures are the most basic device structures and the easiest waveguide schemes to implement, possessing significant application value in the fields of signal optical communication and planar optical waveguide mode signal optical switching. It mainly consists of input / output straight waveguides, asymmetric directional coupling, phase-modulated straight waveguides, and asymmetric Y-branch structures. Its modulation principle is achieved by using the asymmetric directional coupling structure to modulate the E... 11 and E 21 The modes are coupled into two phase modulation waveguides with equal power. Each phase modulation waveguide consists of two parallel straight waveguides and two asymmetric Y-branches. The signal light entering the two phase modulation waveguides is converted from the initially input mode through the cascaded asymmetric Y-branches (E...). 11 Mode conversion to E 21 Pattern, E 21 Mode conversion to mode E 11 ), thereby achieving E 11 Pattern and E 21 The mode modulation insensitive function is further enhanced by an asymmetric directional coupling structure and an asymmetric Y branch, so that the final output mode is the same as the input mode, thereby achieving the function of a switch that is insensitive to the modulation of two optical modes of signals.

[0008] This invention uses a silicon wafer as a substrate and polymers with different refractive indices as the cladding and core materials of the optical waveguide, respectively. The polymer material used to fabricate the core layer has a higher refractive index than the cladding material and exhibits thermal-optical effects. This invention fully utilizes the advantages of polymer materials, such as high thermo-optical coefficients, a wide variety of types, and strong processability. The fabrication process of this invention is simple and compatible with semiconductor processes, enabling large-scale integration and production, thus possessing significant practical application value.

[0009] The technical solution adopted by this invention to solve its technical problem is as follows:

[0010] As attached Figure 1 As shown (for) Figure 2 (Cross-sectional view at position A-A') The modulation-insensitive dual-mode waveguide optical switch of the present invention comprises, from bottom to top, a silicon substrate 51, a polymer lower cladding 52 prepared on the silicon substrate 51 by spin coating, a strip-shaped polymer waveguide core layer 53 prepared on the polymer lower cladding 52 by spin coating, photolithography, and wet etching, a polymer upper cladding 54 prepared on the polymer lower cladding 52 and the polymer waveguide core layer 53 by spin coating, and a metal heating electrode 55 prepared on the polymer upper cladding 54 by vacuum evaporation, spin coating, photolithography, and wet etching; the polymer waveguide core layer 53 is encapsulated within the polymer upper cladding 54.

[0011] As attached Figure 2 As shown, the polymer optical waveguide core layer 53 is composed of a cascaded asymmetric directional coupling waveguide structure and asymmetric Y-branch optical waveguide structure. From left to right along the propagation direction of the signal light, it consists of a first input few-mode straight waveguide 1 and a second input few-mode straight waveguide 2 with the same structure and size (both can transmit E). 11 E 21 (Mode), First Asymmetric Directional Coupled Structure 3 ( Figure 3 ), the first parallel straight waveguide 4 and the second parallel straight waveguide 5 are identical in structure and size and are parallel to each other, the first asymmetric Y-branch 6 and the second asymmetric Y-branch 7 are identical in structure and size. Figure 5 ), a third parallel straight waveguide 8 and a fourth parallel straight waveguide 9 with the same structure and size and parallel to each other, and a second asymmetric directional coupling structure 10. Figure 4 The third asymmetric Y-branch 11 and the fourth asymmetric Y-branch 12 have the same structure and size. Figure 5The system consists of a first output few-mode straight waveguide 13 and a second output few-mode straight waveguide 14 with identical structure and size; a first asymmetric directional coupling structure 3 and a second asymmetric directional coupling structure 10 are symmetrically arranged about the first asymmetric Y-branch 6 and the second asymmetric Y-branch 7; a first heating electrode 15 and a second heating electrode 16 (electrode material is Al, Au or Cr) are respectively fabricated on the polymer cladding 54 directly above the second parallel straight waveguide 5 and the fourth parallel straight waveguide 9, and the first heating electrode 15 and the second heating electrode 16 are collectively referred to as heating electrode 55 (e.g., Figure 1 (As shown).

[0012] As attached Figure 3 As shown, the first asymmetric directional coupling structure 3, from bottom to top along the propagation direction of the signal light, consists of the first S-bend waveguide 17 and the second S-bend waveguide 18 with the same structure and size, the first few-mode straight waveguide 19 and the second few-mode straight waveguide 20 with the same structure and size, the first tapered waveguide 21 and the second tapered waveguide 22, the third few-mode straight waveguide 23 and the fourth few-mode straight waveguide 24, the third tapered waveguide 25 and the fourth tapered waveguide 26, the fifth few-mode straight waveguide 27 and the sixth few-mode straight waveguide 28 with the same structure and size, and the third S-bend waveguide 29 and the fourth S-bend waveguide 30 with the same structure and size.

[0013] As attached Figure 4 As shown, the second asymmetric directional coupling structure 10, from bottom to top along the propagation direction of the signal light, consists of the following components in sequence: the fifth S-bent waveguide 31 and the sixth S-bent waveguide 32, the seventh few-mode straight waveguide 33 and the eighth few-mode straight waveguide 34, the fifth tapered waveguide 35 and the sixth tapered waveguide 36, the ninth few-mode straight waveguide 37 and the tenth few-mode straight waveguide 38, the seventh tapered waveguide 39 and the eighth tapered waveguide 40, the eleventh few-mode straight waveguide 41 and the twelfth few-mode straight waveguide 42, and the seventh S-bent waveguide 43 and the eighth S-bent waveguide 44, all with the same structure and size.

[0014] As attached Figure 5 As shown, the first asymmetric Y branch 6, the second asymmetric Y branch 7, the third asymmetric Y branch 11, and the fourth asymmetric Y branch 12 have the same structure and size. From bottom to top along the propagation direction of the signal light, they are composed of the ninth S-bend waveguide 45 and the tenth S-bend waveguide 46, the ninth tapered waveguide 47 and the tenth tapered waveguide 48, the eleventh S-bend waveguide 49, and the twelfth S-bend waveguide 50.

[0015] In the appendix Figure 2In the circuit, the width W1 of the first input few-mode straight waveguide 1, the second input few-mode straight waveguide 2, the first parallel straight waveguide 4, the second parallel straight waveguide 5, the third parallel straight waveguide 8, the fourth parallel straight waveguide 9, the first output few-mode straight waveguide 13, and the second output few-mode straight waveguide 14 is the same, ranging from 6 to 20 μm; the length L1 of the first input few-mode straight waveguide 1, the second input few-mode straight waveguide 2, the first output few-mode straight waveguide 13, and the second output few-mode straight waveguide 14 is the same (the projected length along the axis of symmetry between the first parallel straight waveguide 4 and the second parallel straight waveguide 5, the same below), ranging from 200 to 2000 μm; the width W of the first heating electrode 15 and the second heating electrode 16 is... E The lengths L2 of the first parallel straight waveguide 4, the second parallel straight waveguide 5, the third parallel straight waveguide 8, the fourth parallel straight waveguide 9, the first heating electrode 15, and the second heating electrode 16 are the same, ranging from 7 to 21 μm;

[0016] In the appendix Figure 3 In the first asymmetric directional coupling structure 3, the coupling spacing G is 1~6μm; the first S-bent waveguide 17, the second S-bent waveguide 18, the first few-mode straight waveguide 19, the second few-mode straight waveguide 20, the connection between the first few-mode straight waveguide 19 and the first tapered waveguide 21, the connection between the second few-mode straight waveguide 20 and the second tapered waveguide 22, the connection between the third tapered waveguide 25 and the fifth few-mode straight waveguide 27, the connection between the fourth tapered waveguide 26 and the sixth few-mode straight waveguide 28, the fifth few-mode straight waveguide 27, the sixth few-mode straight waveguide 28, the third S-bent waveguide 29, and the fourth S-bent waveguide 30 have the same width W1, which is 6~20μm; the first S-bent waveguide 17, the second S-bent waveguide 18, the second S-bent waveguide 19, the second S-bent waveguide 20, the first few-mode straight waveguide 19 and the second tapered waveguide 20, the connection between the fourth tapered waveguide 26 and the sixth few-mode straight waveguide 28, the fifth few-mode straight waveguide 27, the sixth few-mode straight waveguide 28, the third S-bent waveguide 29, and the fourth S-bent waveguide 30 have the same width W1, which is 6~20μm; the first S-bent waveguide 17, the second S-bent waveguide 18, the second S-bent waveguide 19 ... Waveguide 18, the third S-bend waveguide 29, and the fourth S-bend waveguide 30 have the same length L3, ranging from 800 to 2800 μm; the first few-mode straight waveguide 19 and the second few-mode straight waveguide 20 have the same length L4, ranging from 400 to 2000 μm; the width W2 of the connection between the third few-mode straight waveguide 23, the first tapered waveguide 21 and the third few-mode straight waveguide 23, and the connection between the third few-mode straight waveguide 23 and the third tapered waveguide 25 is the same, ranging from 3 to 16 μm; the width W3 of the connection between the fourth few-mode straight waveguide 24, the second tapered waveguide 22 and the fourth few-mode straight waveguide 24, and the connection between the fourth few-mode straight waveguide 24 and the fourth tapered waveguide 26 is the same, ranging from 9 to 24 μm, and W3 > W2; The lengths L5 of the first tapered waveguide 21, the second tapered waveguide 22, the third tapered waveguide 25 and the fourth tapered waveguide 26 are the same, ranging from 200 to 1000 μm; The lengths L6 of the third few-mode straight waveguide 23 and the fourth few-mode straight waveguide 24 are the same, ranging from 50 to 400 μm;

[0017] In the appendix Figure 4In the second asymmetric directional coupling structure 10, the coupling spacing G is 1~6μm; the connection points of the fifth S-bent waveguide 31, the sixth S-bent waveguide 32, the seventh few-mode straight waveguide 33, the eighth few-mode straight waveguide 34, the seventh few-mode straight waveguide 33 and the fifth tapered waveguide 35, the eighth few-mode straight waveguide 34 and the sixth tapered waveguide 36, the seventh tapered waveguide 39 and the eleventh few-mode straight waveguide 41, the eighth tapered waveguide 40 and the twelfth few-mode straight waveguide 42, the eleventh few-mode straight waveguide 41, the twelfth few-mode straight waveguide 42, the seventh S-bent waveguide 43, and the eighth S-bent waveguide 44 have the same width W1, which is 6~20μm; the fifth S-bent waveguide 31, the sixth S-bent waveguide 32, the seventh few-mode straight waveguide 33, the eighth few-mode straight waveguide 34 and the eleventh few-mode straight waveguide 42, the seventh S-bent waveguide 43, and the eighth S-bent waveguide 44 have the same width W1, which is 6~20μm; the fifth S-bent waveguide 31, the sixth S-bent waveguide 32, the seventh few-mode straight waveguide 33, the eleventh few-mode straight waveguide 34, the twelfth few-mode straight waveguide 42, the seventh S-bent waveguide 43, and the eighth S-bent waveguide 44 have the same width W1, which is 6~20μm; the fifth S-bent waveguide 31, the sixth S-bent waveguide 32, the seventh few-mode straight waveguide 33, the eleventh few-mode straight waveguide 34, the t The lengths L3 of the six-S-bent waveguide 32, the seventh-S-bent waveguide 43, and the eighth-S-bent waveguide 44 are the same, ranging from 800 to 2800 μm; the lengths L6 of the seventh few-mode straight waveguide 33 and the eighth few-mode straight waveguide 34 are the same, ranging from 50 to 400 μm; the widths W2 of the connections between the ninth few-mode straight waveguide 37, the fifth tapered waveguide 35 and the ninth few-mode straight waveguide 37, and the ninth few-mode straight waveguide 37 and the seventh tapered waveguide 39 are the same, ranging from 3 to 16 μm; the widths W3 of the connections between the tenth few-mode straight waveguide 38, the sixth tapered waveguide 36 and the tenth few-mode straight waveguide 38, and the tenth few-mode straight waveguide 38 and the eighth tapered waveguide 40 are the same, ranging from 9 to 24 μm, and W3 > W2; The fifth tapered waveguide 35, the sixth tapered waveguide 36, the seventh tapered waveguide 39 and the eighth tapered waveguide 40 have the same length L5, which is 200~1000μm; The eleventh few-mode straight waveguide 41 and the twelfth few-mode straight waveguide 42 have the same length L4, which is 400~2000μm;

[0018] In the appendix Figure 5 In this design, the width W4 of the ninth S-bent waveguide 45, the connection between the ninth S-bent waveguide 45 and the ninth tapered waveguide 47, and the twelfth S-bent waveguide 50 are the same, ranging from 4 to 18 μm; the width W5 of the tenth S-bent waveguide 46, the connection between the tenth S-bent waveguide 46 and the tenth tapered waveguide 48, and the eleventh S-bent waveguide 49 are the same, ranging from 2 to 16 μm; the length L7 of the ninth S-bent waveguide 45, the tenth S-bent waveguide 46, the eleventh S-bent waveguide 49, and the twelfth S-bent waveguide 50 are the same, ranging from 600 to 2600 μm; the length L8 of the ninth tapered waveguide 47 and the tenth tapered waveguide 48 is the same, ranging from 80 to 600 μm; and W1 = W4 + W5;

[0019] The first input few-mode straight waveguide 1, the first S-bend waveguide 17, the first few-mode straight waveguide 19, the first tapered waveguide 21, the third few-mode straight waveguide 23, the third tapered waveguide 25, the fifth few-mode straight waveguide 27, the third S-bend waveguide 29, the first parallel straight waveguide 4, the first asymmetric Y-branch 6, the third parallel straight waveguide 8, the fifth S-bend waveguide 31, the seventh few-mode straight waveguide 33, the fifth tapered waveguide 35, the ninth few-mode straight waveguide 37, the seventh tapered waveguide 39, the eleventh few-mode straight waveguide 41, the seventh S-bend waveguide 43, the third asymmetric Y-branch 11, and the first output few-mode straight waveguide 13 form a cascaded structure; The second input few-mode straight waveguide 2, the second S-bend waveguide 18, the second few-mode straight waveguide 20, the second tapered waveguide 22, the fourth few-mode straight waveguide 24, the fourth tapered waveguide 26, the sixth few-mode straight waveguide 28, the fourth S-bend waveguide 30, the second parallel straight waveguide 5, the second asymmetric Y-branch 7, the fourth parallel straight waveguide 9, the sixth S-bend waveguide 32, the eighth few-mode straight waveguide 34, the sixth tapered waveguide 36, the tenth few-mode straight waveguide 38, the eighth tapered waveguide 40, the twelfth few-mode straight waveguide 42, the eighth S-bend waveguide 44, the fourth asymmetric Y-branch 12, and the second output few-mode straight waveguide 14 form a cascaded structure.

[0020] E 11 Pattern (E) 21 The signal light (in the first input few-mode straight waveguide 1 or the second input few-mode straight waveguide 2) is input from the first input few-mode straight waveguide 1. After passing through the first asymmetric directional coupling structure 3 (whose working principle is basically the same as that of traditional symmetric directional coupling: if two waveguides are close to each other and the effective refractive indices of the transmission modes between the waveguides are similar, there is an energy exchange between the transmission modes between the waveguides, and coupling will occur between the modes, that is, light is coupled from one waveguide to another. The difference is that in asymmetric directional coupling, due to the different widths and spacing of the waveguides, the coupling coefficients are also different. The bandwidth of the device can be increased through the asymmetric structure), the E signal light is then transmitted to the first asymmetric directional coupling structure 3. 11 Pattern (E) 21 The signal light (in the same mode) is coupled into two phase modulation waveguides with equal power (the phase modulation waveguides consist of a first parallel straight waveguide 4, a first asymmetric Y-branch 6, a second parallel straight waveguide 5, and a second asymmetric Y-branch 7). The signal light entering the first parallel straight waveguide 4 and the second parallel straight waveguide 5 is controlled by E... 11 Pattern (E) 21 The mode is converted to E through the first asymmetric Y branch 6 and the second asymmetric Y branch 7. 21 Pattern (E) 11 (During mode conversion, the phase remains unchanged; the working principle of mode conversion in asymmetric Y-branching is the adiabatic evolution of the mode, that is, a mode can gradually evolve into another mode with the closest effective refractive index through asymmetric Y-branching.) Figure 5 As shown, when entering the first asymmetric Y branch 6, E11 Pattern (E) 21 When the signal light of the (mode) propagates to the bifurcation point, based on the optimal matching effective refractive index law, it will evolve into the E in the ninth S-bend waveguide 45. 11 Mode (E in the 10th S-curved waveguide 46) 11 (Mode). Subsequently, E in the ninth S-bend waveguide 45 11 The mode gradually evolved into the E mode in the eleventh S-curved waveguide 49. 11 Mode (E in the 10th S-curved waveguide 46) 11 The mode gradually evolved into the E mode in the 12th S-curved waveguide 50. 11 (mode), which then evolved into the first asymmetric Y branch 6 output terminal E 21 Pattern (E) 11 (pattern), enabling E 11 Pattern (E) 21 (Mode) to E 21 Pattern (E) 11 (Mode conversion). When no modulation is applied, the signal light passing through the phase modulation waveguide remains in phase and enters the second asymmetric directional coupling structure 10 in the converted mode. The second asymmetric directional coupling structure 10 (the working principle of the second asymmetric directional coupling structure 10 is the same as that of the first asymmetric directional coupling structure 3) couples all the signal light into the third asymmetric Y branch 11, and the third asymmetric Y branch 11 performs mode conversion again, outputting signal light from the first output few-mode straight waveguide 13 with the same input mode as the second input few-mode straight waveguide 2; the signal light output through the first asymmetric directional coupling structure 3 is transmitted in the first parallel straight waveguide 4 and the second parallel straight waveguide 5 in the initially input mode, and the first heating element... A voltage is applied to electrode 15 to modulate the signal light in the second parallel straight waveguide 5, changing its phase by π / 2. The signal light then undergoes mode conversion after passing through the second asymmetric Y-branch 7 and enters the fourth parallel straight waveguide 9. A voltage is applied to the second heating electrode 16 to further modulate the converted mode, changing its phase by π / 2. Due to the phase change (the sum of the two phase changes is π), the second asymmetric directional coupling structure 10 couples all the signal light into the fourth asymmetric Y-branch 12, where it undergoes another mode conversion and is output from the second output few-mode straight waveguide 14. Although the phase modulation of the two modes differs when the same temperature is applied to the heating electrode, this design ensures that regardless of the input E... 11 Mode is still E 21 In this mode, the total phase change at the phase modulation waveguide is the same (i.e., the sum of the two phase changes is π), thus achieving the function of dual-mode modulation insensitivity.

[0021] The thickness of the silicon substrate 51 is 0.5~3 mm, the thickness of the polymer lower cladding layer 52 is 3~15 μm, the thickness of the polymer waveguide core layer 53 is 3~15 μm, the thickness of the polymer upper cladding layer 54 is 3~17 μm (the thickness of the polymer upper cladding layer above the polymer waveguide core layer), and the thickness of the heating electrode 55 is 50~400 nm.

[0022] The fabrication process of the modulation-insensitive dual-mode waveguide optical switch described in this invention is shown in the attached figure. Figure 6 Specifically, it is described as follows:

[0023] A: Cleaning of silicon wafer substrates

[0024] Gently wipe the silicon substrate 51 with cotton balls soaked in acetone and ethanol respectively, rinse with deionized water and dry with nitrogen gas, then place it in a clean petri dish and seal it for storage.

[0025] B: Preparation of the polymer lower cladding layer

[0026] A polymer undercoating material (which includes a series of transparent organic polymer materials such as polycarbonate (PC), polyimide (PI), polystyrene (PS), polyethylene (PE), polyester (PET), and EpoClad)) is spin-coated onto a cleaned silicon wafer substrate to form a polymer undercoating film at a spin speed of 1000~5000 rpm. The spin-coated polymer undercoating film is then heated at 90~140 °C for 5~20 minutes, and then exposed to ultraviolet light at a wavelength of 350~400 nm for 3~30 seconds. After exposure, it is heated again at 90~140 °C for 20~60 minutes to obtain a polymer undercoating 52 with a thickness of 3~15 μm on the silicon wafer substrate 51.

[0027] C: Fabrication of the polymer optical waveguide core layer

[0028] A polymer waveguide core material with a negative thermo-optic coefficient (the waveguide core material is a series of wet-etchable ultraviolet negative photoresist materials, including EpoCore, SU-8 2002, and SU-8 2005, with a refractive index higher than that of the polymer cladding material) is spin-coated onto the polymer lower cladding 52 to form a polymer waveguide core film. The spin-coating speed is 700–5000 rpm, and the thickness of the polymer waveguide core film is 3–15 μm. The spin-coated polymer waveguide core film is pre-baked using a stepped heating method, i.e., heated at 50–100 °C for 3–20 minutes, then heated at 80–120 °C for 3–20 minutes, and then cooled to 50–80 °C. The polymer waveguide core film is then photolithographically ... Figure 2 As shown in the figure, the polymer waveguide core layer structure to be prepared is exposed to ultraviolet light at a wavelength of 350~400 nm for 5~30 seconds. After photolithography, it is heated at 50~100 ℃ for 3~20 minutes, and then heated at 80~120 ℃ for 5~30 minutes for intermediate baking. After heating, it is cooled to 20~30 ℃. After cooling, development is performed. First, wet etching is carried out in the developer corresponding to the waveguide core layer material for 5~60 seconds to remove the unexposed non-waveguide core layer structure. Then, it is placed in isopropanol to wash away the unexposed waveguide core layer material and developer remaining on the device surface. Then, it is rinsed with deionized water (rinsing should be done in the direction of the waveguide to prevent damage to the waveguide) to remove the isopropanol on the device surface. It is then dried with nitrogen. Finally, post-baking hardening is performed at 120~160 ℃. Heating at ℃ for 30-60 minutes, a strip-shaped polymer waveguide core layer 53 was thus formed on the polymer lower cladding layer 52;

[0029] D: Preparation of the polymer overcoat

[0030] A polymer top cladding material (which includes a series of transparent organic polymer materials such as polycarbonate (PC), polyimide (PI), polystyrene (PS), polyethylene (PE), polyester (PET), and EpoClad, etc., and uses the same material for both the polymer bottom cladding and the polymer top cladding in the same device) is spin-coated onto the polymer bottom cladding 52 and the polymer waveguide core layer 53 to form a polymer top cladding film. The spin-coating speed is 700~5000 rpm. The spin-coated polymer top cladding film is then heated at 90~140 °C for 5~20 minutes. The polymer top cladding film is then exposed to ultraviolet light at a wavelength of 350~400 nm for 3~30 seconds. After exposure, it is heated again at 90~140 °C for 20~60 minutes to obtain a polymer top cladding 54 with a thickness of 3~17 μm (the thickness of the polymer top cladding above the polymer waveguide core layer).

[0031] E: Preparation of heating electrode

[0032] A heating electrode film with a thickness of 50-400 nm was deposited on the polymer overlay 54 using a vacuum evaporation process. Then, a positive photoresist BP 212 film with a thickness of 1-3 µm was spin-coated onto the heating electrode film at a rotation speed of 1000-3000 rpm. The device with the spin-coated positive photoresist BP 212 film was heated at 70-100 °C for 10-30 minutes, and then cooled to 20-30 °C. Finally, a photolithography process was performed, using a mask with the same structure as the heating electrode to be fabricated (e.g., ...). Figure 2 As shown in the figure, the device is exposed to ultraviolet light with a wavelength of 350-400 nm for 1-5 seconds to expose the photoresist BP 212 film in areas other than the heating electrode. After exposure, the device is immersed in a NaOH solution with a mass concentration of 2-5‰ for 10-60 seconds to remove the exposed photoresist BP 212 film. Then, it is rinsed with deionized water and dried with nitrogen. The device is then heated again at 80-120 °C for 10-30 minutes, and then cooled to 20-30 °C. The heating electrode is then developed by immersing the device in a NaOH solution with a mass concentration of 2-5‰ for 1-15 minutes to remove the electrode film in areas other than the heating electrode. The device is then rinsed repeatedly with deionized water and dried with nitrogen. Finally, the device is immersed in ethanol for 3-10 seconds to remove the unexposed photoresist BP 212 on the heating electrode. The device is then rinsed with deionized water and dried with nitrogen, thus obtaining the modulation-insensitive dual-mode waveguide optical switch described in this invention.

[0033] Compared with existing device structures and fabrication technologies, the advantages of this invention are as follows: The modulation-insensitive dual-mode waveguide optical switch of this invention utilizes the advantages of asymmetric directional coupling structure, simple asymmetric Y-branch structure, and high thermo-optic coefficient of organic polymer materials. By using the asymmetric Y-branch for mode switching during modulation of the heated electrode, insensitive modulation switching of two signal optical modes is achieved. In addition, the use of polymer materials simplifies the device fabrication process, requiring only conventional processes such as spin coating, photolithography, and wet etching, effectively reducing production costs, improving device production efficiency, and facilitating large-scale mass production, enabling the application of this mode signal optical switch in practical applications. Attached Figure Description

[0034] Figure 1 : A schematic cross-sectional view of the modulation-insensitive dual-mode waveguide optical switch described in this invention;

[0035] Figure 2 : A schematic diagram of the modulation-insensitive dual-mode waveguide optical switch of the present invention;

[0036] Figure 3 : Figure 2 A schematic diagram of the first asymmetric directional coupling structure 3 in the middle;

[0037] Figure 4 : Figure 2 A schematic diagram of the second asymmetric directional coupling structure 10 in the middle;

[0038] Figure 5 : Figure 2 Schematic diagrams of the asymmetric Y-branch structures 6, 7, 11, and 12;

[0039] Figure 6 Flowchart of the fabrication process for a modulation-insensitive dual-mode waveguide optical switch;

[0040] Figure 7 (a): Modulation-insensitive dual-mode waveguide optical switch with input E at ΔT=0 K 11 Simulation diagram of signal optical field transmission at the output end of the mode;

[0041] Figure 7 (b): Modulation-insensitive dual-mode waveguide optical switch with input E at ΔT=0 K 11 Simulation diagram of signal optical field distribution in the mode;

[0042] Figure 7 (c): Modulation-insensitive dual-mode waveguide optical switch with input E at ΔT=8 K 11 Simulation diagram of signal optical field transmission at the output end of the mode;

[0043] Figure 7(d): Modulation-insensitive dual-mode waveguide optical switch with input E at ΔT=8 K 11 Simulation diagram of signal optical field distribution in the mode;

[0044] Figure 8 (a): Modulation-insensitive dual-mode waveguide optical switch with input E at ΔT=0 K 21 Simulation diagram of signal optical field transmission at the output end of the mode;

[0045] Figure 8 (b): Modulation-insensitive dual-mode waveguide optical switch with input E at ΔT=0 K 21 Simulation diagram of signal optical field distribution in the mode;

[0046] Figure 8 (c): Modulation-insensitive dual-mode waveguide optical switch with input E at ΔT=8 K 21 Simulation diagram of signal optical field transmission at the output end of the mode;

[0047] Figure 8 (d): Modulation-insensitive dual-mode waveguide optical switch with input E at ΔT=8 K 21 Simulation diagram of signal optical field distribution in the mode;

[0048] Figure 9 Modulation-insensitive dual-mode waveguide optical switches are input to E respectively. 11 and E 21 The output during the mode varies with the heating temperature ΔT of the first heating electrode 15 and the second heating electrode 16;

[0049] Figure 10 Modulation-insensitive dual-mode waveguide optical switch at ΔT=0 K and ΔT=8 K input E 11 In mode, the output curve varies with wavelength;

[0050] Figure 11 Modulation-insensitive dual-mode waveguide optical switch at ΔT=0 K and ΔT=8 K input E 21 In mode, the output curve varies with wavelength; Detailed Implementation

[0051] Example 1

[0052] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0053] As attached Figure 1 As shown (for) Figure 2(Cross-sectional view at position A-A'), from bottom to top, consists of a silicon substrate 51, a polymer lower cladding layer 52 prepared on the silicon substrate 51 by spin coating, a strip-shaped polymer waveguide core layer 53 prepared on the polymer lower cladding layer 52 by spin coating, photolithography, and wet etching, a polymer upper cladding layer 54 prepared on the polymer waveguide core layer 53 by spin coating, and a first heating electrode 15 and a second heating electrode 16 prepared on the polymer upper cladding layer 54 by vacuum evaporation, photolithography, and wet etching. The electrode material is Al, and the first heating electrode 15 and the second heating electrode 16 are collectively referred to as the Al heating electrode 55. The thickness of the silicon substrate 51 is 1 mm, the thickness of the polymer lower cladding layer 52 is 5 μm, the thickness of the polymer waveguide core layer 53 is 5 μm, the thickness of the polymer upper cladding layer 54 is 5 μm (the thickness of the portion above the polymer waveguide core layer 53), and the thickness of the Al heating electrode 55 is 200 nm.

[0054] In the appendix Figure 2 In the circuit, the width W1 of the first input few-mode straight waveguide 1, the second input few-mode straight waveguide 2, the first parallel straight waveguide 4, the second parallel straight waveguide 5, the third parallel straight waveguide 8, the fourth parallel straight waveguide 9, the first output few-mode straight waveguide 13, and the second output few-mode straight waveguide 14 is the same, which is 9μm; the length L1 of the first input few-mode straight waveguide 1, the second input few-mode straight waveguide 2, the first output few-mode straight waveguide 13, and the second output few-mode straight waveguide 14 is the same, which is 1000μm; the width W of the first heating electrode 15 and the second heating electrode 16 is... E The lengths L2 of the first parallel straight waveguide 4, the second parallel straight waveguide 5, the third parallel straight waveguide 8, the fourth parallel straight waveguide 9, the first heating electrode 15, and the second heating electrode 16 are the same, at 2000 μm.

[0055] In the appendix Figure 3In the first asymmetric directional coupling structure 3, the coupling spacing G is 2.7 μm; the first S-bent waveguide 17, the second S-bent waveguide 18, the first few-mode straight waveguide 19, the second few-mode straight waveguide 20, the connection points of the first few-mode straight waveguide 19 and the first tapered waveguide 21, the connection points of the second few-mode straight waveguide 20 and the second tapered waveguide 22, the connection points of the third tapered waveguide 25 and the fifth few-mode straight waveguide 27, the connection points of the fourth tapered waveguide 26 and the sixth few-mode straight waveguide 28, the fifth few-mode straight waveguide 27, the sixth few-mode straight waveguide 28, the third S-bent waveguide 29, and the fourth S-bent waveguide 30 all have the same width W1, which is 9 μm; the first S-bent waveguide 17, the second S-bent waveguide 18, the third S-bent waveguide 29, and the fourth S-bent waveguide 30 all have the same length L3, which is 15 μm. 00μm; the length L4 of the first few-mode straight waveguide 19 and the second few-mode straight waveguide 20 is the same, which is 1100μm; the width W2 of the connection between the third few-mode straight waveguide 23, the first tapered waveguide 21 and the third few-mode straight waveguide 23, and the connection between the third few-mode straight waveguide 23 and the third tapered waveguide 25 is the same, which is 8μm; the width W3 of the connection between the fourth few-mode straight waveguide 24, the second tapered waveguide 22 and the fourth few-mode straight waveguide 24, and the connection between the fourth few-mode straight waveguide 24 and the fourth tapered waveguide 26 is the same, which is 10μm; the length L5 of the first tapered waveguide 21, the second tapered waveguide 22, the third tapered waveguide 25 and the fourth tapered waveguide 26 is the same, which is 460μm; the length L6 of the third few-mode straight waveguide 23 and the fourth few-mode straight waveguide 24 is the same, which is 200μm;

[0056] In the appendix Figure 4In the second asymmetric directional coupling structure 10, the coupling spacing G is 2.7 μm; the connections between the fifth S-bent waveguide 31, the sixth S-bent waveguide 32, the seventh few-mode straight waveguide 33, the eighth few-mode straight waveguide 34, the seventh few-mode straight waveguide 33 and the fifth tapered waveguide 35, the eighth few-mode straight waveguide 34 and the sixth tapered waveguide 36, the seventh tapered waveguide 39 and the eleventh few-mode straight waveguide 41, the eighth tapered waveguide 40 and the twelfth few-mode straight waveguide 42, the eleventh few-mode straight waveguide 41, the twelfth few-mode straight waveguide 42, the seventh S-bent waveguide 43, and the eighth S-bent waveguide 44 are all 9 μm wide; the lengths L3 of the fifth S-bent waveguide 31, the sixth S-bent waveguide 32, the seventh S-bent waveguide 43, and the eighth S-bent waveguide 44 are all 9 μm wide. 1500μm; the length L6 of the seventh few-mode straight waveguide 33 and the eighth few-mode straight waveguide 34 is the same, which is 200μm; the width W2 of the connection between the ninth few-mode straight waveguide 37, the fifth tapered waveguide 35 and the ninth few-mode straight waveguide 37, and the connection between the ninth few-mode straight waveguide 37 and the seventh tapered waveguide 39 is the same, which is 8μm; the width W3 of the connection between the tenth few-mode straight waveguide 38, the sixth tapered waveguide 36 and the tenth few-mode straight waveguide 38, and the connection between the tenth few-mode straight waveguide 38 and the eighth tapered waveguide 40 is the same, which is 10μm; the length L5 of the fifth tapered waveguide 35, the sixth tapered waveguide 36, the seventh tapered waveguide 39 and the eighth tapered waveguide 40 is the same, which is 460μm; the length L4 of the eleventh few-mode straight waveguide 41 and the twelfth few-mode straight waveguide 42 is the same, which is 1100μm;

[0057] In the appendix Figure 5 In the above, the width W4 of the ninth S-bent waveguide 45, the connection between the ninth S-bent waveguide 45 and the ninth tapered waveguide 47, and the twelfth S-bent waveguide 50 is the same, which is 6.1 μm; the width W5 of the tenth S-bent waveguide 46, the connection between the tenth S-bent waveguide 46 and the tenth tapered waveguide 48, and the eleventh S-bent waveguide 49 is the same, which is 2.9 μm; the length L7 of the ninth S-bent waveguide 45, the tenth S-bent waveguide 46, the eleventh S-bent waveguide 49, and the twelfth S-bent waveguide 50 is the same, which is 1300 μm; the length L8 of the ninth tapered waveguide 47 and the tenth tapered waveguide 48 is the same, which is 300 μm.

[0058] In the appendix Figure 6 In the figure, 51 is the silicon wafer substrate, 52 is the polymer lower cladding layer prepared by spin coating, 53 is the polymer waveguide core layer prepared by spin coating, photolithography and wet etching, 54 is the polymer upper cladding layer prepared by spin coating, and 55 is the heating electrode.

[0059] like Figure 7 As shown in (a), when the input is E 11In the mode, at ΔT = 0 K (ΔT represents the temperature change of the heating electrode before and after applying voltage), E 11 The signal light of the mode is input from the second input few-mode straight waveguide 2, and after passing through the first asymmetric directional coupling structure 3, the signal light is coupled into the two phase modulation waveguides with equal power. The signal light entering the first parallel straight waveguide 4 and the second parallel straight waveguide 5 is controlled by E. 11 The pattern is transformed into E after passing through the first asymmetric Y branch 6 and the second asymmetric Y branch 7. 21 The signal light enters the second asymmetric directional coupling structure 10 through the third parallel straight waveguide 8 and the fourth parallel straight waveguide 9. The second asymmetric directional coupling structure 10 couples all the signal light into the third asymmetric Y-branch 11, and the third asymmetric Y-branch 11 then couples the E signal into the third asymmetric Y-branch 11. 21 Mode conversion to E 11 The mode is set to output from the first output few-mode straight waveguide 13, with the switch in the Cross state, and the intensity of the output signal light is the same as the intensity of the input signal light.

[0060] like Figure 7 As shown in (b), when the input is E 11 In the mode, at ΔT = 0 K (ΔT represents the temperature change of the heating electrode before and after applying voltage), E 11 The signal light of the mode is input from the second input few-mode straight waveguide 2, and after passing through the first asymmetric directional coupling structure 3, the signal light is coupled into the two phase modulation waveguides with equal power. The signal light from the first parallel straight waveguide 4 and the second parallel straight waveguide 5 is fed by E 11 The pattern is transformed into E after passing through the first asymmetric Y branch 6 and the second asymmetric Y branch 7. 21 The signal light enters the second asymmetric directional coupling structure 10 after passing through the third parallel straight waveguide 8 and the fourth parallel straight waveguide 9. The second asymmetric directional coupling structure 10 couples all the signal light into the third asymmetric Y-branch 11, and the third asymmetric Y-branch 11 then couples the E signal into the third asymmetric Y-branch 11. 21 Mode conversion to E 11 The mode is set to output from the first output few-mode straight waveguide 13, with the switch in the Cross state. The mode of the output signal light is the same as the mode of the input signal light.

[0061] like Figure 7 As shown in (c), when the input is E 11 The pattern, at ΔT=8 K, E 11 The signal light of the mode is input from the second input few-mode straight waveguide 2, and after passing through the first asymmetric directional coupling structure 3, the signal light is coupled into the two phase modulation waveguides with equal power, at E 11 The mode propagates in the first parallel straight waveguide 4 and the second parallel straight waveguide 5, and the first heating electrode 15 is paired with E. 11The phase of the mode is modulated (phase change π / 2), and the signal light entering the first parallel straight waveguide 4 and the second parallel straight waveguide 5 is controlled by E. 11 The pattern is transformed into E through the first asymmetric Y branch 6 and the second asymmetric Y branch 7. 21 The signal light is then fed into the third parallel straight waveguide 8 and the fourth parallel straight waveguide 9. The second heating electrode 16 modulates the phase after mode conversion, thereby changing the phase (phase change π / 2). The second asymmetric directional coupling structure 10 couples all the signal light into the fourth asymmetric Y branch 12, where mode conversion is performed again, and E is output from the second output few-mode straight waveguide 14. 11 In this mode, with the switch in the Bar state, the intensity of the output signal light is the same as the intensity of the input signal light.

[0062] like Figure 7 As shown in (d), when the input is E 11 The pattern, at ΔT=8 K, E 11 The signal light of the mode is input from the second input few-mode straight waveguide 2, and after passing through the first asymmetric directional coupling structure 3, the signal light is coupled into the two phase modulation waveguides with equal power, at E 11 The mode propagates in the first parallel straight waveguide 4 and the second parallel straight waveguide 5, and the first heating electrode 15 is paired with E. 11 The phase of the mode is modulated, and the signal light entering the first parallel straight waveguide 4 and the second parallel straight waveguide 5 is controlled by E. 11 The pattern is transformed into E through the first asymmetric Y branch 6 and the second asymmetric Y branch 7. 21 The signal light is then fed into the third parallel straight waveguide 8 and the fourth parallel straight waveguide 9. The second heating electrode 16 modulates the phase of the converted mode, thereby changing the phase (phase change π / 2). The second asymmetric directional coupling structure 10 couples all the signal light into the fourth asymmetric Y branch 12, where the mode is converted again, and E is output from the second output few-mode straight waveguide 14. 11 In the mode, with the switch in the Bar state, the output signal light pattern is the same as the input signal light pattern. When modulated or unmodulated, only the output signal port changes; the intensity may slightly change due to losses, but the pattern remains the same.

[0063] like Figure 8 As shown in (a), when the input is E 21 The pattern, at ΔT=0 K, E 21 The signal light of the mode is input from the second input few-mode straight waveguide 2, and after passing through the first asymmetric directional coupling structure 3, the signal light is coupled into the two phase modulation waveguides with equal power. The signal light entering the first parallel straight waveguide 4 and the second parallel straight waveguide 5 is controlled by E. 21The pattern is transformed into E after passing through the first asymmetric Y branch 6 and the second asymmetric Y branch 7. 11 The signal light enters the second asymmetric directional coupling structure 10 after passing through the third parallel straight waveguide 8 and the fourth parallel straight waveguide 9. The second asymmetric directional coupling structure 10 couples all the signal light into the third asymmetric Y-branch 11, and the third asymmetric Y-branch 11 then couples the E signal into the third asymmetric Y-branch 11. 11 Mode conversion to E 21 The mode is set to output from the first output few-mode straight waveguide 13, with the switch in the Cross state, and the intensity of the output signal light is the same as the intensity of the input signal light.

[0064] like Figure 8 As shown in (b), when the input is E 21 The pattern, at ΔT=0 K, E 21 The signal light of the mode is input from the second input few-mode straight waveguide 2, and after passing through the first asymmetric directional coupling structure 3, the signal light is coupled into the two phase modulation waveguides with equal power. The signal light entering the first parallel straight waveguide 4 and the second parallel straight waveguide 5 is controlled by E. 21 The pattern is transformed into E after passing through the first asymmetric Y branch 6 and the second asymmetric Y branch 7. 11 The signal light enters the second asymmetric directional coupling structure 10 after passing through the third parallel straight waveguide 8 and the fourth parallel straight waveguide 9. The second asymmetric directional coupling structure 10 couples all the signal light into the third asymmetric Y-branch 11, and the third asymmetric Y-branch 11 then couples the E signal into the third asymmetric Y-branch 11. 11 Mode conversion to E 21 The mode is set to output from the first output few-mode straight waveguide 13, with the switch in the Cross state. The mode of the output signal light is the same as the mode of the input signal light.

[0065] like Figure 8 As shown in (c), when the input is E 21 The pattern, at ΔT=8 K, E 21 The signal light of the mode is input from the second input few-mode straight waveguide 2, and after passing through the first asymmetric directional coupling structure 3, the signal light is coupled into the two phase modulation waveguides with equal power, at E 21 The mode propagates in the first parallel straight waveguide 4 and the second parallel straight waveguide 5, and the first heating electrode 15 is paired with E. 21 The phase of the mode is modulated (phase change π / 2), and the signal light entering the first parallel straight waveguide 4 and the second parallel straight waveguide 5 is controlled by E. 21 The pattern is transformed into E through the first asymmetric Y branch 6 and the second asymmetric Y branch 7. 11The signal light is then fed into the third parallel straight waveguide 8 and the fourth parallel straight waveguide 9. The second heating electrode 16 modulates the phase after mode conversion, thereby changing the phase (phase change π / 2). The second asymmetric directional coupling structure 10 couples all the signal light into the fourth asymmetric Y branch 12, where mode conversion is performed again, and E is output from the second output few-mode straight waveguide 14. 21 In this mode, with the switch in the Bar state, the intensity of the output signal light is the same as the intensity of the input signal light.

[0066] like Figure 8 As shown in (d), when the input is E 21 The pattern, at ΔT=8 K, E 21 The signal light of the mode is input from the second input few-mode straight waveguide 2, and after passing through the first asymmetric directional coupling structure 3, the signal light is coupled into the two phase modulation waveguides with equal power, at E 21 The mode propagates in the first parallel straight waveguide 4 and the second parallel straight waveguide 5, and the first heating electrode 15 is paired with E. 21 The phase of the mode is modulated (phase change π / 2), and the signal light entering the first parallel straight waveguide 4 and the second parallel straight waveguide 5 is controlled by E. 21 The pattern is transformed into E through the first asymmetric Y branch 6 and the second asymmetric Y branch 7. 11 The signal light is then fed into the third parallel straight waveguide 8 and the fourth parallel straight waveguide 9. The second heating electrode 16 modulates the phase after mode conversion, thereby changing the phase (phase change π / 2). The second asymmetric directional coupling structure 10 couples all the signal light into the fourth asymmetric Y branch 12, where mode conversion is performed again, and E is output from the second output few-mode straight waveguide 14. 21 In the mode, with the switch in the Bar state, the output signal light pattern is the same as the input signal light pattern. When modulated or unmodulated, only the output signal port changes; the intensity may slightly change due to losses, but the pattern remains the same.

[0067] like Figure 9 As shown, when ΔT=0 K, the input E 11 and E 21 In mode, the output of the Cross port is almost 0 dB; at ΔT = 8 K, the input E 11 and E 21 In the mode, the output of the Cross port is less than -28 dB, while the output of the Bar port is almost 0 dB. It can be seen that when the first heating electrode 15 and the second heating electrode 16 are heated, the signal light in both modes can achieve the switching function, and when the heating temperature is 8 K, the signal light cancellation ratio in both modes is greater than 28 dB.

[0068] like Figure 10 As shown, input E at ΔT=0 K and ΔT=8 K 11 The output versus wavelength curves in the mode show that when ΔT = 0 K, the Cross port output is almost 0 dB and hardly changes with wavelength. The Bar port output is less than -17 dB in the wavelength range of 1510 nm-1570 nm, and the output is not sensitive to wavelength changes. When ΔT = 8 K, the Bar port output is almost 0 dB and hardly changes with wavelength. The Cross port output is less than -16 dB in the wavelength range of 1510 nm-1570 nm, and the output is not sensitive to wavelength changes.

[0069] like Figure 11 As shown, input E at ΔT=0 K and ΔT=8 K 21 The output versus wavelength curves in the mode show that when ΔT = 0 K, the Cross port output is almost 0 dB and hardly changes with wavelength. The Bar port output is less than -17 dB in the wavelength range of 1510 nm-1570 nm, and the output is not sensitive to wavelength changes. When ΔT = 8 K, the Bar port output is almost 0 dB and hardly changes with wavelength. The Cross port output is less than -16 dB in the wavelength range of 1510 nm-1570 nm, and the output is not sensitive to wavelength changes.

[0070] Example 2:

[0071] Device fabrication, such as Figure 6 As shown.

[0072] Cleaning of silicon substrate 51: Gently wipe the silicon substrate with cotton balls soaked in acetone and ethanol respectively, rinse with deionized water and dry with nitrogen gas, then place it in a clean petri dish and seal it for storage.

[0073] The polymer undercoating layer 52 was prepared using a spin-coating process: the EpoClad polymer undercoating material was spin-coated onto a cleaned silicon wafer substrate at a spin speed of 4000 rpm; then the spin-coated polymer film was heated at 120°C for 10 minutes; the polymer film was then exposed to ultraviolet light at a wavelength of 365 nm for 15 seconds; after exposure, it was heated again at 140°C for 30 minutes, thus obtaining the polymer undercoating layer 52 on the silicon wafer substrate with a thickness of 5 μm.

[0074] The polymer waveguide core layer, including the input / output region, asymmetric directional coupling region, phase modulation region, and asymmetric Y-branch region, was fabricated using spin coating, photolithography, and wet etching processes. Specifically, EpoCore, a polymer waveguide core material with a negative thermo-optic coefficient, was spin-coated onto the device with a polymer cladding layer to form a thin film at a spin speed of 4000 rpm, resulting in a polymer film thickness of 5 μm. The spin-coated polymer film was then pre-baked using a stepped heating method: heating at 60 ℃ for 5 minutes, followed by heating at 95 ℃ for 10 minutes, and then cooling to 60 ℃. Photolithography was then performed on the polymer waveguide core layer film, with the waveguide mask structure complementary to the desired polymer waveguide core layer structure (e.g., ...). Figure 2 As shown, the waveguide core material of the device to be fabricated is exposed to ultraviolet light at a wavelength of 365 nm for 18 seconds, so that the input / output region, asymmetric directional coupling region, phase modulation region, and asymmetric Y-branch region of the device are exposed to ultraviolet light. After photolithography, intermediate baking is performed, which is heated at 60 °C for 5 minutes and then at 85 °C for 10 minutes. After heating, the temperature is cooled to 25 °C. Then, development is performed. First, wet etching is performed in the developer corresponding to the waveguide core material for 50 seconds to remove the unexposed non-waveguide core structure. Then, the device is placed in isopropanol to wash away the unexposed waveguide core material and developer remaining on the device surface. Then, it is rinsed with deionized water (rinsing should be done in the direction of the waveguide to prevent damage to the waveguide) to remove the isopropanol on the device surface. Then, it is dried with nitrogen. Finally, post-baking hardening is performed, which is heated at 140 °C for 30 minutes. In this way, a strip-shaped polymer waveguide core layer 53 is fabricated on the polymer lower cladding 52.

[0075] The polymer cladding layer 54 was prepared using a spin-coating process: EpoClad polymer cladding material was spin-coated onto the device with the pre-fabricated polymer waveguide core layer at a spin-coating speed of 4000 rpm, resulting in a polymer film thickness of 5 μm. The spin-coated polymer film was then heated at 120 °C for 10 minutes. The entire polymer film was then exposed to ultraviolet light at a wavelength of 365 nm for 20 seconds. After exposure, it was heated again at 140 °C for 30 minutes, thus obtaining the polymer cladding layer 54 on the device.

[0076] An Al heating electrode was fabricated using vacuum evaporation, spin coating, photolithography, and wet etching processes. A 200 nm thick Al heating electrode film was deposited on a polymer overlay using vacuum evaporation. Then, a positive photoresist BP 212 was spin-coated onto the Al heating electrode film at a spin speed of 2500 rpm, resulting in a BP 212 film with a thickness of 2 µm. The device with the spin-coated BP 212 was heated to 87 °C for 20 minutes, and then cooled to 25 °C. A photolithography process was then performed, using a mask with the same structure as the heating electrode to be fabricated (e.g., [image of mask]). Figure 2 As shown, the device is exposed to ultraviolet light at a wavelength of 365 nm for 2 seconds to expose the photoresist BP 212 film in areas other than the heating electrode. The device is then immersed in a 5‰ NaOH solution for 20 seconds to remove the exposed photoresist BP 212, rinsed with deionized water, and dried with nitrogen. The device is then heated again at 95 °C for 10 minutes, followed by cooling to 25 °C. The Al heating electrode is then developed by immersing the device in a 5‰ NaOH solution for 5 minutes to remove the Al heating electrode film in areas other than the heating electrode. The device is then repeatedly rinsed with deionized water and dried with nitrogen. Finally, the device is immersed in ethanol for 5 seconds to remove the unexposed photoresist BP 212 on the Al heating electrode, rinsed with deionized water, and dried with nitrogen, thus obtaining the modulation-insensitive dual-mode waveguide optical switch described in this invention.

[0077] This results in the fabrication of a modulation-insensitive dual-mode waveguide optical switch that meets the requirements. It should be noted that although this patent document contains descriptions of many details, it should not be construed as limiting the scope or potential claims of any disclosed technology, but rather as a description of features specific to particular embodiments that may be specific to the disclosed technology. The invention can also be modified in many ways, such as using waveguide materials like lithium niobate, silicon, and silicon nitride. What is readily apparent to those skilled in the art from the explicit disclosure of this invention or from the undisputed written description is within the scope of protection of this patent.

Claims

1. A modulation-insensitive dual-mode waveguide optical switch, characterized in that: From bottom to top, it consists of a silicon substrate (51), a polymer lower cladding (52), a polymer waveguide core layer (53), and a polymer upper cladding (54). The polymer waveguide core layer (53) is encased within the polymer upper cladding (54). The refractive index of the polymer waveguide core layer (53) is higher than that of the polymer upper cladding (54) and the polymer lower cladding (52). The polymer waveguide core layer (53) is composed of a cascaded asymmetric directional coupling waveguide structure and an asymmetric Y-branch waveguide structure. From left to right along the propagation direction of the signal light, it consists of a first input few-mode straight waveguide (1) and a second input few-mode straight waveguide (2) with the same structure and size, a first asymmetric directional coupling structure (3), a first parallel straight waveguide (4) and a second parallel straight waveguide (5) with the same structure and size and parallel to each other, a first asymmetric Y-branch (6) and a second asymmetric Y-branch (6) with the same structure and size. The structure consists of a branch (7), a third parallel straight waveguide (8) and a fourth parallel straight waveguide (9) of the same structure and size and parallel to each other, a second asymmetric directional coupling structure (10), a third asymmetric Y branch (11) and a fourth asymmetric Y branch (12) of the same structure and size, a first output few-mode straight waveguide (13) and a second output few-mode straight waveguide (14) of the same structure and size; the first asymmetric directional coupling structure (3) and the second asymmetric directional coupling structure (10) are symmetrically arranged about the first asymmetric Y branch (6) and the second asymmetric Y branch (7), and a first heating electrode (15) and a second heating electrode (16) are respectively fabricated on the polymer cladding (54) directly above the second parallel straight waveguide (5) and the fourth parallel straight waveguide (9); by using the asymmetric Y branch to perform mode conversion when the heating electrode is modulated, an insensitive modulation switch for the optical modes of the two signals is realized; The first asymmetric directional coupling structure (3) is composed of, along the propagation direction of the signal light, a first S-bend waveguide (17) and a second S-bend waveguide (18) of the same structure and size, a first few-mode straight waveguide (19) and a second few-mode straight waveguide (20) of the same structure and size, a first tapered waveguide (21) and a second tapered waveguide (22), a third few-mode straight waveguide (23) and a fourth few-mode straight waveguide (24), a third tapered waveguide (25) and a fourth tapered waveguide (26), a fifth few-mode straight waveguide (27) and a sixth few-mode straight waveguide (28) of the same structure and size, and a third S-bend waveguide (29) and a fourth S-bend waveguide (30) of the same structure and size; The second asymmetric directional coupling structure (10) is composed of, along the propagation direction of the signal light, the fifth S-bent waveguide (31) and the sixth S-bent waveguide (32) with the same structure and size, the seventh few-mode straight waveguide (33) and the eighth few-mode straight waveguide (34) with the same structure and size, the fifth tapered waveguide (35) and the sixth tapered waveguide (36), the ninth few-mode straight waveguide (37) and the tenth few-mode straight waveguide (38), the seventh tapered waveguide (39) and the eighth tapered waveguide (40), the eleventh few-mode straight waveguide (41) and the twelfth few-mode straight waveguide (42) with the same structure and size, and the seventh S-bent waveguide (43) and the eighth S-bent waveguide (44) with the same structure and size; The first asymmetric Y branch (6), the second asymmetric Y branch (7), the third asymmetric Y branch (11), and the fourth asymmetric Y branch (12) have the same structure and size. They are composed of the ninth S-bend waveguide (45) and the tenth S-bend waveguide (46), the ninth tapered waveguide (47) and the tenth tapered waveguide (48), the eleventh S-bend waveguide (49), and the twelfth S-bend waveguide (50) in sequence along the direction of signal light propagation.

2. The modulation-insensitive dual-mode waveguide optical switch as described in claim 1, characterized in that: The first input few-mode straight waveguide (1), the first S-bend waveguide (17), the first few-mode straight waveguide (19), the first tapered waveguide (21), the third few-mode straight waveguide (23), the third tapered waveguide (25), the fifth few-mode straight waveguide (27), the third S-bend waveguide (29), the first parallel straight waveguide (4), the first asymmetric Y-branch (6), the third parallel straight waveguide (8), the fifth S-bend waveguide (31), the seventh few-mode straight waveguide (33), the fifth tapered waveguide (35), the ninth few-mode straight waveguide (37), the seventh tapered waveguide (39), the eleventh few-mode straight waveguide (41), the seventh S-bend waveguide (43), the third asymmetric Y-branch (11), and the first output few-mode straight waveguide (13) form a cascaded structure; The second input few-mode straight waveguide (2), the second S-bend waveguide (18), the second few-mode straight waveguide (20), the second tapered waveguide (22), the fourth few-mode straight waveguide (24), the fourth tapered waveguide (26), the sixth few-mode straight waveguide (28), the fourth S-bend waveguide (30), the second parallel straight waveguide (5), the second asymmetric Y-branch (7), the fourth parallel straight waveguide (9), the sixth S-bend waveguide (32), the eighth few-mode straight waveguide (34), the sixth tapered waveguide (36), the tenth few-mode straight waveguide (38), the eighth tapered waveguide (40), the twelfth few-mode straight waveguide (42), the eighth S-bend waveguide (44), the fourth asymmetric Y-branch (12), and the second output few-mode straight waveguide (14) form a cascaded structure.

3. The modulation-insensitive dual-mode waveguide optical switch as described in claim 1, characterized in that: The width W1 of the first input few-mode straight waveguide (1), the second input few-mode straight waveguide (2), the first parallel straight waveguide (4), the second parallel straight waveguide (5), the third parallel straight waveguide (8), the fourth parallel straight waveguide (9), the first output few-mode straight waveguide (13), and the second output few-mode straight waveguide (14) is the same, ranging from 6 to 20 μm; the length L1 of the first input few-mode straight waveguide (1), the second input few-mode straight waveguide (2), the first output few-mode straight waveguide (13), and the second output few-mode straight waveguide (14) is the same, ranging from 200 to 2000 μm; the width W of the first heating electrode (15) and the second heating electrode (16) is the same. E The lengths L2 of the first parallel straight waveguide (4), the second parallel straight waveguide (5), the third parallel straight waveguide (8), the fourth parallel straight waveguide (9), the first heating electrode (15), and the second heating electrode (16) are the same, ranging from 7 to 21 μm.

4. The modulation-insensitive dual-mode waveguide optical switch as described in claim 1, characterized in that: The coupling spacing G of the first asymmetric directional coupling structure (3) is 1~6μm; the first S-bent waveguide (17), the second S-bent waveguide (18), the first few-mode straight waveguide (19), the second few-mode straight waveguide (20), the connection between the first few-mode straight waveguide (19) and the first tapered waveguide (21), the connection between the second few-mode straight waveguide (20) and the second tapered waveguide (22), the connection between the third tapered waveguide (25) and the fifth few-mode straight waveguide (27), the connection between the fourth tapered waveguide (26) and the sixth few-mode straight waveguide (28), the fifth few-mode straight waveguide (27), the sixth few-mode straight waveguide (28), the third S-bent waveguide (29), and the fourth S-bent waveguide (30) have the same width W1, which is 6~20μm; the first S-bent waveguide (17), the second S-bent waveguide (18), the second S-bent waveguide (19), the second S-bent waveguide (20), the second S-bent waveguide (21), the second S-bent waveguide (22), the third S-bent waveguide (25), the second S-bent waveguide (27), the third S-bent waveguide (29), and the fourth S-bent waveguide (30) have the same width W1, which is 6~20μm; the first S-bent waveguide (17), the second S-bent waveguide (28), the second S-bent waveguide (29), and the third ... The lengths L3 of the curved waveguide (18), the third S-curved waveguide (29), and the fourth S-curved waveguide (30) are the same, ranging from 800 to 2800 μm; the lengths L4 of the first few-mode straight waveguide (19) and the second few-mode straight waveguide (20) are the same, ranging from 400 to 2000 μm; the widths W2 of the third few-mode straight waveguide (23), the connection between the first tapered waveguide (21) and the third few-mode straight waveguide (23), and the connection between the third few-mode straight waveguide (23) and the third tapered waveguide (25) are the same, ranging from 3 to 16 μm; the widths W3 of the fourth few-mode straight waveguide (24), the connection between the second tapered waveguide (22) and the fourth few-mode straight waveguide (24), and the connection between the fourth few-mode straight waveguide (24) and the fourth tapered waveguide (26) are the same, ranging from 9 to 24 μm, and W3 > W2; The lengths L5 of the first tapered waveguide (21), the second tapered waveguide (22), the third tapered waveguide (25) and the fourth tapered waveguide (26) are the same, ranging from 200 to 1000 μm; The lengths L6 of the third few-mode straight waveguide (23) and the fourth few-mode straight waveguide (24) are the same, ranging from 50 to 400 μm.

5. A modulation-insensitive dual-mode waveguide optical switch as described in claim 1, characterized in that: The coupling spacing G of the second asymmetric directional coupling structure (10) is 1~6μm; the width W1 of the fifth S-bent waveguide (31), the sixth S-bent waveguide (32), the seventh few-mode straight waveguide (33), the eighth few-mode straight waveguide (34), the connection between the seventh few-mode straight waveguide (33) and the fifth tapered waveguide (35), the connection between the eighth few-mode straight waveguide (34) and the sixth tapered waveguide (36), the connection between the seventh tapered waveguide (39) and the eleventh few-mode straight waveguide (41), the connection between the eighth tapered waveguide (40) and the twelfth few-mode straight waveguide (42), the eleventh few-mode straight waveguide (41), the twelfth few-mode straight waveguide (42), the seventh S-bent waveguide (43), and the eighth S-bent waveguide (44) is the same, which is 6~20μm; the fifth S-bent waveguide (31) The lengths L3 of the sixth S-bent waveguide (32), the seventh S-bent waveguide (43), and the eighth S-bent waveguide (44) are the same, ranging from 800 to 2800 μm; the lengths L6 of the seventh few-mode straight waveguide (33) and the eighth few-mode straight waveguide (34) are the same, ranging from 50 to 400 μm; the widths W2 of the ninth few-mode straight waveguide (37), the connection between the fifth tapered waveguide (35) and the ninth few-mode straight waveguide (37), and the connection between the ninth few-mode straight waveguide (37) and the seventh tapered waveguide (39) are the same, ranging from 3 to 16 μm; the widths W3 of the tenth few-mode straight waveguide (38), the connection between the sixth tapered waveguide (36) and the tenth few-mode straight waveguide (38), and the connection between the tenth few-mode straight waveguide (38) and the eighth tapered waveguide (40) are the same, ranging from 9 to 24 μm, and W3 > W2; The lengths L5 of the fifth tapered waveguide (35), the sixth tapered waveguide (36), the seventh tapered waveguide (39) and the eighth tapered waveguide (40) are the same, ranging from 200 to 1000 μm; The lengths L4 of the eleventh few-mode straight waveguide (41) and the twelfth few-mode straight waveguide (42) are the same, ranging from 400 to 2000 μm.

6. The modulation-insensitive dual-mode waveguide optical switch as described in claim 1, characterized in that: The width W4 of the ninth S-bent waveguide (45), the connection between the ninth S-bent waveguide (45) and the ninth tapered waveguide (47), and the twelfth S-bent waveguide (50) is the same, ranging from 4 to 18 μm; the width W5 of the tenth S-bent waveguide (46), the connection between the tenth S-bent waveguide (46) and the tenth tapered waveguide (48), and the eleventh S-bent waveguide (49) is the same, ranging from 2 to 16 μm; the length L7 of the ninth S-bent waveguide (45), the tenth S-bent waveguide (46), the eleventh S-bent waveguide (49), and the twelfth S-bent waveguide (50) is the same, ranging from 600 to 2600 μm; the length L8 of the ninth tapered waveguide (47) and the tenth tapered waveguide (48) is the same, ranging from 80 to 600 μm; and W1 = W4 + W5.

7. The modulation-insensitive dual-mode waveguide optical switch as described in claim 1, characterized in that: The thickness of the silicon substrate (51) is 0.5~3 mm, the thickness of the polymer lower cladding (52) is 3~15 μm, the thickness of the polymer waveguide core layer (53) is 3~15 μm, the thickness of the polymer upper cladding (54) above the polymer waveguide core layer (53) is 3~17 μm, and the thickness of the heating electrode (55) is 50~400 nm.

8. The modulation-insensitive dual-mode waveguide optical switch as described in claim 1, characterized in that: The materials of the polymer lower cladding (52) and the polymer upper cladding (54) are one of polycarbonate, polyimide, polystyrene, polyethylene, polyester, and EpoClad. The materials of the polymer optical waveguide core layer (53) are one of EpoCore, SU-8 2002, and SU-8 2005. The materials of the first heating electrode (15) and the second heating electrode (16) are Al, Au, or Cr. In the same device, the materials of the polymer lower cladding (52) and the polymer upper cladding (54) are the same, and the materials of the first heating electrode (15) and the second heating electrode (16) are the same.

9. A method for fabricating a modulation-insensitive dual-mode waveguide optical switch according to any one of claims 1 to 8, comprising the following steps: A: Cleaning of silicon wafer substrates Gently wipe the silicon substrate (51) with cotton balls soaked in acetone and ethanol respectively, rinse with deionized water and dry with nitrogen gas; B: Preparation of the polymer lower cladding layer The polymer undercoating material is spin-coated onto a cleaned silicon wafer substrate (51) to form a polymer undercoating film using a spin-coating process at a speed of 1000~5000 rpm; Then the spin-coated polymer undercoat film is heated at 90~140 ℃ for 5~20 minutes, and then exposed to ultraviolet light with a wavelength of 350~400 nm for 3~30 seconds. After exposure, it is heated again at 90~140 ℃ for 20~60 minutes, thereby obtaining the polymer undercoat (52) on the silicon wafer substrate 51. C: Fabrication of the polymer optical waveguide core layer A polymer waveguide core layer material with a negative thermo-optic coefficient was spin-coated onto the polymer cladding (52) to form a polymer waveguide core layer film. The spin-coating speed was 700~5000 rpm. The spin-coated polymer waveguide core layer film was pre-baked using a stepped heating method, that is, heated at 50~100 ℃ for 3~20 minutes, then heated at 80~120 ℃ for 3~20 minutes, and then cooled to 50~80 ℃. The polymer waveguide core layer film was then photolithographically ... ℃; After cooling, development is performed, that is, wet etching is first performed in the developer corresponding to the waveguide core material for 5~60 seconds to remove the unexposed non-waveguide core structure, and then it is placed in isopropanol to wash away the unexposed waveguide core material and developer remaining on the device surface, and then rinsed with deionized water to remove the isopropanol on the device surface, and then dried with nitrogen; finally, post-baking is performed, that is, heating at 120~160 ℃ for 30~60 minutes, so as to obtain the strip-shaped polymer waveguide core (53) on the polymer lower cladding (52). D: Preparation of the polymer overcoat The polymer upper cladding material is spin-coated onto the polymer lower cladding (52) and the polymer waveguide core layer (53) to form a polymer upper cladding film. The spin-coating speed is 700~5000 rpm. Then the spin-coated polymer upper cladding film is heated at 90~140 ℃ for 5~20 minutes. The polymer upper cladding film is then exposed to ultraviolet light at a wavelength of 350~400 nm for 3~30 seconds. After exposure, it is heated again at 90~140 ℃ for 20~60 minutes to obtain the polymer upper cladding (54). E: Preparation of heating electrode A heating electrode film was deposited on the polymer cladding (54) using a vacuum evaporation process. Then, a positive photoresist BP 212 film with a thickness of 1~3 µm was spin-coated on the heating electrode film at a rotation speed of 1000~3000 rpm. The device with the spin-coated positive photoresist BP 212 film was heated at 70~100 ℃ for 10~30 minutes. After heating, the temperature was lowered to 20~30 ℃. Then, a photolithography was performed. The structure of the photomask was the same as that of the heating electrode to be prepared. The photomask was exposed under ultraviolet light with a wavelength of 350~400 nm for 1~5 seconds, so that the photoresist BP212 film in areas other than the heating electrode was exposed. After exposure, the device is placed in a NaOH solution with a mass concentration of 2-5‰ for 10-60 seconds to remove the exposed photoresist BP 212 film. Then, it is rinsed with deionized water and dried with nitrogen. The device is then heated again at 80-120 °C for 10-30 minutes, followed by cooling to 20-30 °C. The heating electrodes are then developed by immersing the device in a 2-5‰ NaOH solution for 1-15 minutes to remove the electrode film outside the heating electrodes. The device is then repeatedly rinsed with deionized water and dried with nitrogen. Finally, the device is immersed in ethanol for 3-10 seconds to remove the unexposed photoresist BP 212 on the heating electrodes, rinsed again with deionized water, and dried with nitrogen, thus obtaining the modulation-insensitive dual-mode waveguide optical switch.

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